Diaquabis(5-carboxy-2-propyl-1H-imidazole-4-carboxylato-κ2N3,O4)nickel(II) tetrahydrate

In the title complex, [Ni(C8H9N2O4)2(H2O)2]·4H2O, the NiII ion is coordinated in a slightly distorted octahedral environment formed by two bis-chelating H2pimda (H3pimda is 2-propyl-1H-4,5-dicarboxylic acid) ligands and two coordinated water molecules. In the crystal structure, a three-dimensional framework is formed by intermolecular O—H...O and N—H...O hydrogen bonds involving the solvent water molecules, coordinated water molecules, carboxylate O atoms and the protonated N atoms of the H2pimda ligands. The propyl groups of each H2pimda ligand are disordered over two sets of sites with refined occupancies of 0.50 (2):0.50 (2) and 0.762 (11):0.238 (11). In one water solvent molecule, one of the H atoms was refined as disordered over two sites of equal occupancy.